The temperature and wind atmospheric data are important parameters in the calculations. The flight management systems of the prior art offer the pilot the possibility of defining a temperature profile throughout a flight plan via the definition of altitude/temperature pairings at a number of waypoints of the altitude profile. A wind profile can also be defined by direction/intensity pairings on a number of flight levels. These data are input by the pilot from information that he receives during the flight, notably the meteorological information at the arrival airport. However, these data are obtained from probes measurements that may be old because the wind data are generally entered when preparing the flight and are rarely updated again. They therefore significantly differ from the dynamic data measured by the onboard sensors. Aircraft manufacturers therefore want the measured meteorological data to be regularly integrated into the flight plan prediction calculation. Integrating raw data at a defined frequency, which represents the state of the art, presents the drawback of creating discontinuities from one leg to another in front of the aeroplane and notably falsifying the transition calculations between legs.